Germanium may be divided from metals by fractional distillation of volatile germanium tetrachloride, which is then hydrolyzed to deliver GeO2. The dioxide is actually reduced with hydrogen to give the actual element. Area refining techniques permit the production of ultra-pure germanium. Germanium can be found in argyrodite (a sulfide of germanium and silver), in germanite (made up of about 8% of the element), in coal, within zinc ores, and other minerals. The actual element may be commercially prepared from the flue dusts off of smelters digesting zinc ores or even from the by-products from the combustion of certain hot coals.